Shotgun cartridge



Feb. 18, 1941;

H. A. ROBERTS ETAL SHOTGUN CARTRIDGE Filed July 22, 1936 2 Sheets-Sheet2 v v w 3 J u y, 1 fimw I 1.24; v l

PatentedFeb. 18, 1941 PATENT OFFICE SHOTGUN CARTRIDGE llorace AinleyRoberts, Huddersfield, and William Dickson, Streetly, EnglandApplication July 22, 1936, Serial No. 91,980 In Great Britain August 12,1935 9 Claims.

This invention relates to shotgun cartridges, and the manufacturethereof, and, more particularly to the closing and sealing of the mouthof the cartridge case.

Hitherto the mouth of the cartridge case has been closed and the shotretained in position with the aid of a cardboard disc (hereinafterreferred to as the over-shot card) which is held in position by turningor folding over the edge of the mouth of the case in such a manner thata retaining rim is pressed on to the disc. Cartridges made in thismanner, however, have been found subject to deterioration owing to thefact that under certain conditions moisture permeates into the interiorof the cartridge which not only causes swelling of the wads but alsoaffects the moisture content of the powder charge with deleteriousefiects upon the ballistics of the cartridge.

Cartridges made from rolled paper tubes which are closed in the mannerdescribed, have been waterproofed in various ways, usually by dippingthe loaded cartridge in a waterproofiing lacquer. Unless specialprecautions are taken, however, the film of lacquer is liable to crackand its waterproofing properties are destroyed. It has been proposed towaterproof the end closure by covering the overshot card and the crevicebetween the card and the turned-over edge of the case with a coating ofwaterproof material, e. g. shellac or cellulose varnish. It has beenfound that cartridges treated in this manner are not entirelysatisfactory, since the lacquer does not always form an efficient bondbetween the paper tubular portion and the overshot card, with the resultthat small cracks are formed which permit a certain amount of moistureto enter the cartridge case with consequent deleterious'results. It hasalso been proposed to make the tubular portion of the cartridge casefrom an entirely waterproof material such as Celluloid, but the use ofhighly inflammable material such as Celluloid in this art is to be dep-.

recated. Proposals have also been made to mould the tubular portion andthe head of the cartridge case from plastic materials having waterproofproperties, but these proposals have not described any solution of theproblem of providing a completely waterproof end closure for thecartridge.

The present invention has for an object to provide cartridges of highballistic efliciency in which the cartridge case and closure thereof are.formed in a simple and effective manner to provide a completelywaterproof assembly.

The present invention involves the production of a shotgun cartridgeincluding a moulded tubular casing portion consisting of a substantiallynon-inflammable waterproof plastic material, the mouth of which issealed by a waterproof plastic closure, either integrally .moulded orbonded by fusion to the said tubular portion, or firmly united theretowith the aid of an auxiliary waterproof adhesive joining the plasticmaterial of the closure and the plastic material of the tubular portion.The plastic material, in addition to being highly waterproof, should benonbrittle and capable of being shaped by a moulding operation. Thus,for example, thermoplastic materials, such as those containing celluloseethers, or cellulose esters such as cellulose acetate, together withsuitable plasticisers and fillers, may be used. In particular we preferto employ the compositions described and claimed in U. S. Patent2,137,350. The arrangement is preferably such that the plastic materialextends in an unbroken manner throughout the whole of the tubularportion and end closure, which thus constitute an integral unit. Thismay be carried out by softening the plastic material of the side Wallsof the tubular portion and the end closure by the application of heatand/or a solvent, pressure being preferably applied to complete thebonding action.

Alternatively, the tubular portion and the end closure may be moulded inthe form of a single cup-shaped unit, and in this case the flanged baseportion which is made separate from the tubular portion is joined to thelatter in a.waterproof manner, after the cartridge case has been loaded,by means of a suitable cement or by softening the contacting portions bythe application of heat or a solvent. In a further alternative method ofcarrying out our invention, the end closure is united with the tubularportion of the case by turningover the side walls of the case on to aplastic disc and sealing the joint so formed with a waterproof cement oradhesive between the contacting surfaces.

It will be understood that our invention is not limited to cartridgecases in which the end closure is formed wholly of plastic material asthe end closure may comprise a disc formed partly of a. plasticcomposition and partly of cardboard or like material. Where a compositedisc is used, however, it is essential that the plastic side wall of thecase shall be bonded with or made to adhere to the plastic portion ofthe said disc. The moulded side walls of the case, moreover, may bereinforced with paper, fabric or other suitable material. Furthermore,the invention is not limited to the use of the same plastic material forthe tubular portion and the end closure, as difi'erent plastic materialsmay, if desired, be used for these two parts of the case provided thatthe bond between the components is waterproof and suificiently strong to,provide the necessary ballistic properties of the cartridge.

Various methods of carrying out our invention are illustrated in theaccompanying drawings in which:

Figure 1 is a sectional elevation of a cartridge constructed inaccordance with our invention.

Figure 2 is a perspective view of the cartridge showing one stage in themouth closing opera tion.

Figure 3 is a diagrammatic part sectional elevation of an apparatus forcarrying out the final closing operation.

Figure 4 is a sectional elevation of the mouth of a cartridge showing agroove formed in the tubular portion of the case.

Figure 5 is a sectional elevation of the mouth of a cartridge showing anannular groove formed in the end closure.

Figure 6 is a sectional elevation of the mouth of a cartridge showing analternative form of end closure.

Figure 7 is a sectional elevation of the mouth of a cartridge showingyet a further form of end closure.

Figure 8 is a sectional elevation of a cartridge showing an alternativeconstruction.

Figure 9 is a perspective view of a charged cartridge showing the end ofthe case turned over onto an overshot card preparatory to theapplication of heat and pressure.

Referring to Figures 1 to 3 of the drawings, the numeral I denotes acartridge case which is moulded in a suitable pressure moulding orinjection moulding press, not shown in the drawings, from anon-inflammable plastic material of the kind described containingcellulose ethers, or esters such as cellulose acetate, together with oneor more plasticisers, e. g. tri-phenyl phosphate,

tricresyl phosphate, diamyl tartrate or di-ethylphthalate and a suitablefiller. e. g. French chalk. The cartridge is provided with a priming cap2 and is loaded with a powder charge 3, a wad 4 and a shot charge 5. Inthe process of manufacture an overshot card 5 is inserted in thecartridge and the end of the case is crimped into the form of a shorttruncated cone 1, as shown in Figure 2, by means of a suitable crimpingtool, not shown in the drawings.

In order finally to close and seal the mouth of the cartridge, thelatter is placed in a suitably supported metal die 8, as shown in Figure3, the base of the cartridge being supported by a removable block 9which allows the cartridge to be inserted into and removed from the die.The die is maintained at normal room temperature by means of coolingwater which is circulated through channels l0. A concentric punch II,which is suitably guided by means of guides I 2, is lowered in thedirection of arrow A and is pressed into firm contact with the crimpededge of the case by means of either a dead weight, a suitable weightedlever mechanism or a hydraulic ram, not shown on the drawings. The punchII is heated by passing steam through channels I3 and the heated punchcauses the thermoplastic material to soften and flow over the overshotcard 6, thus sealing the mouth of the case wi ha end closure l4(Figure 1) consisting of a layer of homogeneous material of substantialthickness.

When the heated punch II has been in contact with the end of the casefor a suilicient length of time to cause softening and flow of thematerial, the steam supply to the punch is cut ofi" and a quantity ofcold water is circulated through the channels l3, thus chilling andsetting the thermoplastic material and enabling the-cartridge to beremoved from the die. The punch II is reduced in diameter at itsextremity I5 to provide a step, the purpose of which is to form anupstanding flange "5 at the end of the cartridge case, as shown inFigure- 1. The flatannular surface of the punch l I, indicated by thenumeral I! of Figure 3. is arranged to contact with the edge of theflange I 6 so that a smooth square edge free from any moulding flash isprovided.

. The bursting pressure of the cartridge may be adjusted by varying thethickness of the material above the overshot card. This may convenientlybe. carried out by regulating the length of the cartridge case allottedfor turn-over. It will be understood that as the turned-over portion isspread over the whole area of the end of the case a comparatively largevariation in the length of the turned-over portion results in quite asmall variation in thickness of the plastic material covering theovershot card. Thus, any small variation in the length of theturned-over portion such as may occur in practice due to inequalities inthe depth of the wad, or in the quantity of powder or shot charge,afl'ects the thickness of the plastic covering to such a small extentthat the bursting pressure is unaffected and remains constant for anygiven setting of the turn-over and the loading pressure.

In order to locate definitely the position at which bursting of thecartridge takes place, a peripheral groove l8 may be provided in theside wall of the case, as shown in Figure 4. This may be convenientlycarried out after the sealing operation by means of a revolving cutteror like tool. The depth of the groove may be regulated to give anydesired bursting pressure, and the provision of such a groove ensuresthat a particularly clean cut edge is formed at the end of the caseafter firing. Instead of making the groove in the side .wall of thecase, an annular groove may be provided in the end closure, adjacent thesurrounding tubular portion of the case as shown at 19, in Figure 5.This groove may conveniently be formed or pressed into the external faceof the closure wall during the sealing operation, by providing aprojecting annular ring (not shown) on the end of the punch II. Ifdesired, the end of the punch which comes into contact with the mouth ofthe case may be suitably embossed with letters or figures denoting thetrade-mark, shot size or the like.

It will be understood that the apparatus illustrated diagrammatically inFigure 3 may be adapted to seal the ends of a number of cartridges byarranging a plurality of punches which are operated simultaneously inconjunction with a corresponding number of dies. Our improved method ofclosing the mouth of the cartridge may be further adapted to massproduction methods by feeding the cartridges automatically and insuccession into the dies by means of asuitable conveyor system.

Instead of crimping the end of the case to provide the necessaryturn-over-this may be accomplished by turning over'the edge in thenormal manner with the aid of a rotary turnover tool,

as will be understood from Figure 9, after which the turned-over edge issubjected to pressure and heat in the manner previously described, sothat the plastic material is made to flow over the whole surface of theovershot card to form a homogeneous layer.

In Figure 9, the case is indicated at l and the overshot card at 6.

In an alternative method of closing the mouth of the cartridge case inaccordance with the present invention the ends 20 of the case are shapedas shown in Figure 6, and a plastic disc 2| is inserted above theovershot card 6. A solvent is applied to the periphery of the disc andthe edge, as indicated at 22 on the drawings, the purpose of the solventbeing to bond the side walls and the disc together. Where plasticmaterials containing cellulose esters or ethers are used a solvent suchas acetone or methylene chloride may be employed. Instead of employing aplastic disc, a quantity of moulding powder may be used which is treatedwith a solvent and applied to the top of the overshot card to form ahomogeneous layer which is bonded to the side walls of the case.Alternatively, the side walls of the case may be turned over and asolvent employed to soften the material and enable same to flow over thewhole surface of the end of the case, pressure being preferably appliedto complete the bonding action. In an alternative method heat andpressure may be used to effect the bonding action of either a separateplastic disc or a moulding powder and, if desired, the end closure maybe moulded or bonded with the side walls of the case without the latterbeing crimped or turned over. Where a separate plastic disc is used thismay be bonded to the side walls of thecase by the application of aheated punch before turning over the free end of the case, the said endbeing subsequently turned over to provide a rounded off finish. Where amoulding powder is used this may be united with the side walls of thecase by means of an injection moulding operation which is carried out byplacing the end of the case in a suitably shaped mould and injectingheated plastic material therein under pressure.

In all of the forms thus far described,-fusion of the plastic endclosure material occurs, heat being employed in some instances, and asolvent in others, as the agency for causing fusion to occur.

In a further modification, as shown in Figure '7, an auxiliarywaterproof adhesive, as indicated at 23, is used to secure the turnedover portion 20 to the plastic surface of the, disc 24. It is essentialfor the formation of a satisfactory waterproof seal that the twosurfaces in contact with the adhesive shall consist of plastic material.

Although a cardboard overshot card is shown in the foregoing drawings,this may be omitted provided that a suitable plastic material is chosenfor the end closure which does not adhere to the shot charge.

In a still further modification, as shown in Figure 8, the tubularportion denoted by the numeral 25 is moulded in the form of a single cupshaped unit with the end closure 26. In a case portion 21 containing thepercussion cap 2. The

base portion is preferably made of moulded plastic material which isfirmly bonded to the side walls of the tubular portion 25 by softeningthe contacting surfaces 28 with ,a suitable solvent. Where the plasticmaterial of the tubular and base portions is of the thermo hardeningtype which is not readily soluble, an auxiliary adhesive may be used tounite the parts together.

We have found that the ballistics of shotgun cartridges made inaccordance with our invention are constant and unvarying over longperiods of service when in hot moist climates, this being due largely tothe fact that a completely waterproof case is obtained. By way ofcomparison it may be mentioned that such cartridges, after having beenimmersed in water for twenty-four hours, showed no appreciable signs ofswelling and the powder moisture remained within the specified limits,whereas the known type of cart ridge having a paper tubular portion withstandard turned-over end and waterproofed by dipping in a solution ofwaterproof material, showed distinct signs of swelling and the powdermoisture exceeded the specified amount. Moreover, our method ofmanufacture enables the loading pressure applied tothe shot and powdercharges and also the bursting pressure of the cartridge to be readilyand accurately controlled, which factors contribute to the increasedballistic efficiency of the cartridge.

As many apparently widely different embodiments of our invention may bemade without departing from the spirit and scope thereof, we do notlimit ourselves to the specific embodiments thereof, except as definedin the appended claims We claim:

1. A method of manufacturing waterproof shotgun cartridges, having abase, a tubular case portion united with said base, and an end closurefor the tubular case, which includes the steps of molding a tubular caseportion and base from substantially non-inflammable, waterproof,nonmetallic, plastic material, placing the powder, wad and shot chargetherein, bringing into position across the discharge end of the tubularcase portion a body of non-inflammable, non-metallic, waterproof,plastic material, and sealing the discharge end by fusion of said endmaterial and by applying external pressure to said end material forcingsuch material against the charge and the case portion to form awaterproof end closure integral with the tubular case portion extendingover the entire area of the end.

2. The method of manufacturing waterproof shotgun cartridges, having atubular case portion provided with a base, and an end-closure for thetubular case portion, which includes the steps of molding the tubularcase portion and base from substantially non-inflammable, waterproof,non-metallic, thermo-plastic material, said tubular body being made longenough to provide both the charge-enclosing wall portion and also anadditional length containing, a surplus of material sufficient to forman end closure, placing the powder, wad, and shot charge in the tubularcase portion, bringing into position, across the discharge end of thetubular case portion, the said surplus material by a bending operation,and sealing the discharge end by fusion of said surplus material andbyapplying external pressure to it forcing such material against thecharge and the case portion to mold it into a complete waterproofend-closure integral with the tubular case portion.

3. A loaded shotgun cartridge comprising a powder-clfarge', a wad, and ashot-charge, an integral waterproof casing including a base portion,

a tubular case portion, and an end-closure portion closing the dischargeend of said tubular case portion, said casing entirely enclosing andsealing said powder, shot charge, and wad therein, said casingconsisting of substantially homogeneous, non-metallic, non-inflammablewaterproof plastic material, said base portion being arranged to receivea primer, said charges being held'under compression by the end-closureportion.

4. A loaded shotgun cartridge comprising a powder-charge, a wad, and ashot-charge, an integral waterproof casing including a base portion,said casing entirely enclosing and sealing said powder, shot charge, andwad therein, a tubular case portion, and an end-closure portion closingthe discharge end of said tubular case portion, said casing consistingof substantially homogeneous, non-metallic, non-inflammable, waterproof,plastic material, said base portion being arranged to receive a primer,said casin having near its discharge end a definite line of weaknessarranged to determine the bursting pressure developed by the cartridgewhen exploded.

5. A loaded shotgun cartridge comprising a powder-charge, a wad, ashot-charge, and an over-shot disc, an integral waterproof casingincluding a base portion, a tubular case portion, and an end-closureportion closing the discharge end of said tubular case portion, saidcasing entirely enclosing and sealing said powder, shot charge, and wadtherein, said casing consisting of substantially homogeneous,non-metallic, noninflammable, waterproof, plastic material, said baseportion-being arranged to receive a 'primer, said over-shot disc beinglocated between the shot-charge and the end-closure whereby adhesionbetween the shot-charge and the end-closure is avoided.

6. The method of manufacturing waterproof shotgun cartridges having atubular case portion provided with a base, and an end-closure for thetubular case portion, whichincludes the steps of molding a tubular bodyfrom substantially non-inflammable, waterproof,- non-metallicthermoplastic material, said tubular body portion being made long enoughto project beyond the charge to provide a surplus of material sufficientto form an end-closure, placing the powder, wad, and shot charge in thetubular case portion, bringing into position across the discharge end ofthe tubular case portion a body of substantially non-inflammable,non-metallic,

thermoplastic material, which comprises placing the charged cartridge ina die, providing at the end to be closed a quantity of the material fromwhich the case is formed sufiicient to form the closure and. pressing on.this material a punch heated to a temperature sufficient to fuse thesaid material, meanwhile maintaining thetemperature of the sides of thecartridge case below the softening points.

8. A method of manufacturing a waterproof end-closure to a cartridge,the case of which is of substantially non-inflammable, non-metallic,thermoplastic material which comprises charging a cartridge which has anelongated case of such length that the material in that part of thecartridge case which projects beyond the charge is suflicient to formthe end-closure, turning over the said projecting portion of thecartridge case inwardly, placing the charged and turned over cartridgein a die and pressing on the turned over end a punch heated to atemperature sufficient to fuse the turned over portion, meanwhilemaintaining the temperature of the sides of the cartridge case below thesoftening point.

9. A method of manufacturing a waterproof end-closure to a cartridge,the case of which is of substantially non-inflammable, non-metallic,thermoplastic material which comprises placing thecharged cartridgehaving an overshot card in a die, placing on the overshot card aquantity of molding powder suflicient .to form the closure and pressingon this molding powder a punch heated to a, temperature suflicient tofuse the molding powder, meanwhile maintaining the temperature of thesides of the cartridge case below the softening point.

HORACE AINLEY ROBERTS. WILLIAM DICKSON.

